Rail assembly

ABSTRACT

A rail assembly includes an outer rail, an intermediate rail, an inner rail, and a retrieving unit. The outer rail has an outer rail space defined therein for receiving the intermediate rail, the inner rail, and the retrieving unit. The intermediate rail is movably received in the outer rail space. The intermediate rail has an intermediate rail space defined therein. The inner rail is movably received in the intermediated rail space. The retrieving unit is disposed in one end of the outer rail space. The retrieving unit includes a fixing member, a sliding rail, a sliding member, a clip, a guiding member, and at least one spring. The fixing member is disposed in the outer rail space to close the outer rail space. The sliding rail is disposed in the fixing member. The sliding rail has a lean rail formed therein. The lean rail has a hold slot defined therein. The sliding member is disposed in the outer rail space. The sliding member moves along the sliding rail and is movably received in the outer rail space. The intermediate rail has an avoiding space defined in an underside thereof such that a length and a moving range of the intermediate rail are increased. The clip is pivotally connected to the sliding member. The guiding member is disposed in the inner rail. The guiding member temporarily engages with the clip to connect the inner rail and the sliding member. The at least one spring is disposed between the fixing member and the sliding member. The fixing member and the sliding member has two avoiding slots respectively defined therein. The inner rail moves in the outer rail space. The inner rail passes the avoiding slots to reach a closed end of the outer rail such that a length of the inner rail is equal to that of the outer rail.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation-in-part Application of Ser. No. 11/905,638, filed 3 Oct. 2007, and entitled “RAIL ASSEMBLY FOR DRAWERS”, now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rail assembly, and more particularly to a rail assembly for drawers.

2. Description of Related Art

A conventional rail assembly is widely used on drawers and generally includes an outer rail, an inner rail and an intermediate rail disposed between the outer rail and the inner rail. The outer rail is fixed to the desk. The inner rail is connected to the side of the drawer. Multiple steel balls are disposed between the intermediate rail and the inner rail such that the drawer pulls out or pushes in easily.

The conventional rail assembly further has a retrieving unit disposed on the bottom of the outer rail to provide an effort of automatic retraction for pushing the intermediate rail and the inner rail in the outer rail. However, the retrieving unit occupies the space of the outer rail. The length of the inner rail and that of the intermediate rail are shorter than that of the outer rail, otherwise the inner rail and the intermediate rail are not completely received in the outer rail. Therefore, the total travel (span) when the outer rail, the intermediate rail and the inner rail expand completely is less the ideal length (span), which is the triple length of the outer rail. If the actual travel (span) approaches to the ideal length (span), the pan ratio is good. Therefore, the short rail assembly has great expanding effort. The intermediate rail and the inner rail are not required to be shortened their length such that the strength of the intermediate rail and the inner rail are not affected. The conventional intermediate rail is cut for receiving a damping mechanism. The conventional rail assembly has a good travel (span) but a poor strength.

A conventional rail assembly in accordance with the prior art shown in FIG. 1 comprises an outer rail 90, an intermediate rail 91, an inner rail 92, a sliding rail 93, and a damper 94. The outer rail 90 has a U cut-shaped section. The outer rail 90 has a stopper 901 and a fixing base 902 disposed in a free end thereof. A sliding space 903 is defined between the outer rail 90 and the stopper 901 and the fixing base 902. The intermediate rail 91 has an opening 910 defined in one end thereof to prevent from interference with the sliding rail 93. The inner rail 92 is received in the sliding space 903 and movably slides relative to the outer rail 90. The inner rail 92 has a clasper 920 disposed in one end thereof and corresponding to the fixing base 902. The sliding rail 93 is fixed to the fixing base 902 and received in the sliding space 903 between the inner rail 92 and the fixing base 902 to form a closed type rail. When the intermediate rail 91 moves toward the fixing base 902, the sliding rail 93 is received in the opening 910. The sliding rail has a positioning hook 930 disposed therein and corresponding to the clasper 920. When the positioning hook 930 engages with the clasper 920, the inner rail 920 is connected to the sliding rail 93 in a predefined distance. The positioning hook 930 is limited by the closed type sliding rail 93. The damper 94 is disposed in the fixing base 902.

The opening 910 in the intermediate rail 91 results in the loss of the length and the strength. Besides, the fixing base 902 (inner rail 92) does not have any structure for fitting the inner rail 92 (opening 910). The inner rail 92 can not extend or retract efficiently. Therefore, the conventional rail assembly has the problem of poor span.

In other aspect, the damper 94 of the conventional rail assembly is disposed in the end of the outer rail 90. The damper 90 has an air chamber and a pushing rod. The pushing rod pushes the air chamber to create the effort of damping. The pushing rod occupies the space of the outer rail 90. When the inner rail 92 automatically retracts, the inner rail 92 abuts against the damper 94 to damp the inner rail 92. Therefore, the length of the inner rail 92 is limited such that the total travel (span) of the rail assembly is limited.

Furthermore, the adaptability between the retrieving unit and the outer rail is another problem. The conventional retrieving unit is used the inner wall of the outer rail as a rail. Therefore, the width of the retrieving unit is equal to that of the inner rail. For the outer rails with different sizes, the different retrieving units are required to fit the outer rails. This is not convenient for warehousing.

The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional rail assembly.

SUMMARY OF THE INVENTION

The main objective of the present invention is to provide an improved rail assembly which provides a steady structure, a good span ratio, and adaptability for different sizes.

To achieve the objective, the rail assembly includes an outer rail, an intermediate rail, an inner rail, and a retrieving unit. The outer rail has an outer rail space defined therein for receiving the intermediate rail, the inner rail, and the retrieving unit. The intermediate rail is movably received in the outer rail space. The intermediate rail has an intermediate rail space defined therein. The inner rail is movably received in the intermediated rail space. The retrieving unit is disposed in one end of the outer rail space. The retrieving unit includes a fixing member, a sliding rail, a sliding member, a clip, a guiding member, and at least one spring. The fixing member is disposed in the outer rail space to close the outer rail space. The sliding rail is disposed in the fixing member. The sliding member has a lean rail formed therein. The lean rail has a hold slot defined therein. The sliding member is disposed in the outer rail space. The sliding member moves along the sliding rail and is movably received in the outer rail space. The intermediate rail has an avoiding space defined in an underside thereof such that a length and a moving range of the intermediate rail are increased. The clip is pivotally connected to the sliding member. The guiding member is disposed in the inner rail. The guiding member temporarily engages with the clip to connect the inner rail and the sliding member. The at least one spring is disposed between the fixing member and the sliding member. The fixing member and the sliding member has two avoiding slots respectively defined therein. The inner rail moves in the outer rail space. The inner rail passes the avoiding slots to reach a closed end of the outer rail such that a length of the inner rail is equal to that of the outer rail.

Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rail assembly in accordance with the prior art;

FIG. 2 is an exploded perspective view of a first embodiment of a rail assembly in accordance with the present invention;

FIG. 3 is an assembled perspective view of the first embodiment of the rail assembly in accordance with the present invention;

FIGS. 4 and 5 show the operation of the first embodiment of the rail assembly in accordance with the present invention;

FIG. 6 is an exploded perspective view of a second embodiment of a rail assembly in accordance with the present invention;

FIGS. 7A-7C show the operation of the second embodiment of the rail assembly in accordance with the present invention;

FIG. 8 is an exploded perspective view of a third embodiment of a rail assembly in accordance with the present invention;

FIG. 9 is a partial enlarged perspective view of in FIG. 8;

FIGS. 10-13 show the operation of the third embodiment of the rail assembly in accordance with the present invention;

FIG. 14 is an exploded perspective view of a fourth embodiment of a rail assembly in accordance with the present invention;

FIG. 15 is an exploded perspective view of a fifth embodiment of a rail assembly in accordance with the present invention;

FIG. 16 is an exploded perspective view of a sixth embodiment of a rail assembly in accordance with the present invention;

FIG. 17 is an assembled perspective view of the sixth embodiment of the rail assembly in accordance with the present invention;

FIG. 18 is an exploded perspective view of a seventh embodiment of a rail assembly in accordance with the present invention;

FIG. 19 is another exploded perspective view of the seventh embodiment of the rail assembly in accordance with the present invention, which is viewed from another orientation;

FIG. 20 is an assembled perspective view of the seventh embodiment of the rail assembly in accordance with the present invention;

FIGS. 21-23 show the operation of the seventh embodiment of the rail assembly in accordance with the present invention; and

FIG. 24 is an exploded perspective view of an eighth embodiment of a rail assembly in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings and initially to FIGS. 1-2, a first embodiment of a rail assembly in accordance with the present invention comprises an outer rail 10, an intermediate rail 20, an inner rail 30, a retrieving unit 40, and a damper 50.

The outer rail 10 has a U-shaped section. The outer rail 10 has an outer rail space 11 defined therein for receiving the intermediate rail 20, the inner rail 30, and the retrieving unit 40. A roller assembly 12 is disposed in the outer rail space 11 such that the intermediate rail 20 is movably connected to the outer rail 10.

The intermediate rail 20 also has a U-shaped section. The width of the intermediate rail 20 is slightly smaller than that of the roller assembly. The intermediate rail 20 is received in the roller assembly 12 to movably connect to the outer rail 10. The intermediate rail 20 is movably received in the outer rail space 11. The intermediate rail 20 has an intermediate rail space 21 defined therein. A roller assembly 22 is disposed in the intermediate rail space 21 such that the inner rail 30 is movably connected to the intermediate rail 20. The intermediate rail 20 has an avoiding space 23 defined in an underside thereof.

The inner rail 30 has a reversed U-shaped section. The inner rail 30 has an inner rail space 31 defined therein. The width of the inner rail 30 is slightly smaller than that of the roller assembly 22 in the intermediate rail space 21. The inner rail 30 is received in the roller assembly 22 such that the inner rail 30 is movably connected to the intermediate rail 20. The inner rail 30 is movably received in the intermediate rail space 21.

The retrieving unit 40 is disposed in one end of the outer rail 10. The retrieving unit 40 includes a fixing member 41, a sliding rail 412, two springs 414, a sliding member 42, and a guiding member 32. The fixing member 41 is stably received in the outer rail space 11. The fixing member 41 has a stop flange 411 formed in one end thereof to close the outer rail space 11. The sliding rail 412 is extended from the other end of the fixing member 41. In this embodiment the sliding rail 412 is connected to the fixing member 41. In other embodiment the sliding rail is formed in the outer rail 10 and near the fixing member 41. The two springs 414 are respectively disposed in two laterals of the fixing member 41. Each spring 414 is connected to the sliding member 42 to provide the sliding member 42 retracted by the resilient force.

The sliding rail 412 is provided for assembling with the sliding member 42 such that the sliding member 42 moves along the sliding rail 412. The sliding rail 412 has a lean rail 4121 formed therein. The lean rail 4121 has a hold slot 413 defined in a front end thereof. The hold slot 413 is provided for temporarily fastening the sliding member 42 with the sliding rail 412. A width of the sliding rail 412 is smaller than that of the avoiding space 23 in the intermediate rail 20. The sliding rail is corresponded to the avoiding space 23 such that the intermediate rail 20 moves free in the outer rail space 11 and is not blocked by the sliding rail 412.

The sliding member 42 moves in the outer rail space 11 due to the disposition of open type sliding rail 412. This increases the retraction travel and sliding range of the intermediate rail 20. Therefore, the total span and the length of the intermediate rail 20 are increased.

Referring to FIGS. 2-3, the sliding member 42 has a clip 421 disposed therein. The clip 421 is pivotally connected to the sliding member 42. The clip 421 has a first (clipping) projection 4211 and a second (stable) projection 4212 respectively formed in an underside thereof. The guiding member 32 is disposed in an inner side of the inner rail 30. The guiding member 32 is a projection structure and is selectively operated with the clip 421. Referring to FIG. 6, when the inner rail 30 overlaps with the sliding member 42, the guiding member 32 engages with the clip 421 such that the inner rail 30 is connected to the sliding member 42 temporarily. The first (clipping) projection 4211 and the second (stable) projection 4212 are provided to cooperate with the lean rail 4121 such that the stability of the sliding member 42 is increased.

When the sliding member 42 is pulled outwardly, the first (clipping) projection 4211 engages with the hold slot 413 such that the sliding member 42 is fastened in the front end of the sliding rail 412. The inner rail 30 disengages with the clip 421 and is pulled out. In the contrast, when the inner rail 30 is pushed inwardly, the guiding member 32 engages with the clip 421. The first (clipping) projection 4211 disengages with the hold slot 413 such that the inner rail 30 is connected to the sliding member 42 to retract. The sliding member 42 has two avoiding slots 422 defined therein. The fixing member 41 has two avoiding slots 415 defined therein. Each avoiding slot 415,422 is corresponded to the inner rail 30 such that the inner rail 30 moves free in the outer rail space 11. This increases the moving range of the inner rail 30. A length of the inner rail 30 is equal to that of the outer rail 10. Therefore, the total span and the loading capability are increased. Each spring 414 is disposed in an outer lateral of each avoiding slot 422 to prevent interference with the inner rail 30.

The damper 50 is fixed in one end of the outer rail. The damper 50 is a pressure bar. One end of the damper 50 is fixed in the fixing member 41. The other end of the damper 50 is abutted against the sliding member 42 to provide the effort of damping. The damper 50 can be any other damping member with different damping coefficient.

Referring to FIGS. 4-5, when the intermediate rail 20 and the inner rail 30 are received in the outer rail space 11, the avoiding space 23 in the intermediate rail 20 is corresponded to the sliding rail 412, such that the intermediate rail 20 is not blocked by the sliding rail 412. The intermediate rail 20 extends closely into the end of the outer rail 10. The inner rail 30 extends into the end of the outer rail 10 due to the avoiding slots 415,422. The inner rail 30 is temporarily connected to the sliding member 42 by the engagement of the guiding member 32 and the clip 421. When the inner rail 30 is pulled outwardly, the sliding member 42 is driven to move along the sliding rail 412. The sliding member 42 moves with the clip 421 and then engages with the hold slot 413. Therefore, the sliding member 42 is fastened with the sliding rail 412 temporarily. The intermediate rail 20 and the inner rail 30 extend into the end of the outer rail 10, therefore, the length of the intermediate rail 20 and that of the inner rail 30 are increased. The total span is increased, so is the ratio of extending length to the retracting length.

Referring to FIGS. 4-5, when the intermediate rail 20 and the inner rail 30 are retracted, the intermediate rail 20 abuts against the sliding member 42 of the retrieving unit 40. When the inner rail 30 overlaps the sliding member 42, the guiding member 32 engages with the clip 421 such that the inner rail 30 is connected to the sliding member 42 temporarily. The sliding member 42 is driven to disengage with the hold slot 413 by the movement of the inner rail 30. When the sliding member 42 disengages with the hold slot 413, the sliding member 42 is retracted toward the end of the outer rail space 11 by the spring 414 force. In the meantime, the damper 50 provides the function of slowing down. Therefore, the sliding member 42 and the inner rail 30 gently move toward the end of the inner rail 10 to prevent the great impact. The inner rail 30 and the intermediate rail 20 move with the sliding member 41 to the end of the outer rail space 11 in a retracting state as shown in FIG. 4.

Referring to FIG. 6, a second embodiment of a rail assembly in accordance with the present invention is illustrated. In the following, only the different between the first embodiment and the second embodiment is described. The rail assembly has a damper unit. The damper unit includes a damper 50 and a stopper 52. The damper 50 is disposed in the avoiding space 23 of the intermediate rail 20. The stopper is disposed in a front end of the sliding rail 412 and corresponding to the damper 50. When the inner rail 30 and the sliding member 42 retract, the damper 50 is blocked by the stopper 52 to provide the function of damping. In other embodiment, the damper is disposed between the intermediate rail 20 and the inner rail space 31. The stopper is disposed in the inner rail space 31.

Referring to the FIGS. 7A-7C, when the inner rail 30 is pushed back, the guiding member 32 engages with the clip 421 such that the clip 421 disengages with the hold slot 413. In the meantime, the inner rail 30 and the sliding member 42 are retracted by the spring 414 force. The damper 50 abuts against the stopper 52 to provide the effort of damping.

The damper 50 is disposed in the avoiding space 23 of the intermediate rail 20, such that the retrieving unit 40 is decreased the length for installing the damper 50. The moving range of the intermediate rail 20 is increased, so is the total travel (span).

In the first embodiment, the sliding member 42 is made of metal and the clip 421 is made of the plastic. In the second embodiment, the sliding member 42 and the clip 421 are made of plastic. In the first and second embodiments, the function and effort of the sliding members 42 are the same.

Referring to FIG. 8, a third embodiment of a rail assembly in accordance with the present invention is illustrated. The rail assembly comprises an outer rail 10, an intermediate rail 20, an inner rail 30, and a retrieving unit 40. The outer rail 10 has an outer rail space 11 defined therein for receiving the intermediate rail 20, the inner rail 30, and the retrieving unit 40. The intermediate rail 20 is movably received in the outer rail space 11. The intermediate rail 20 has an intermediate rail space 21 defined therein for receiving the inner rail 30. The intermediate rail 20 has an avoiding space defined in an underside thereof. The inner rail 30 is movably received in the intermediate rail space 21. The inner rail 30 has a guiding member 32 formed therein.

The retrieving unit 40 includes a fixing member 41, a sliding rail 412, a sliding member 42, a clip 421, and at least one spring 414. The fixing member 41 is disposed in one end of the outer rail space 11 to close the outer rail space 11. The sliding rail 412 is disposed in one end of the fixing member 41. The sliding rail 412 has a lean rail 4121 formed therein. The lean rail 4121 has a hold slot 413 and a slot 413A respectively defined in two laterals thereof. The sliding rail 412 is disposed in the avoiding space 23. The sliding rail 412 is also connected to the fixing member 41. In other embodiment, the sliding rail 412 is disconnected to the fixing member 41. The sliding member 42 is disposed in the outer rail space 11 and moves along the sliding rail 412. The sliding member 42 is movably received in the outer rail space 11 due to the sliding rail 412. The sliding member 42 has a sliding groove 429 defined in an underside thereof and corresponding to the sliding rail 412 such that the sliding member 42 moves along the sliding rail 412. The clip 421 is pivotally connected to the sliding member 42. A connecting pin 43 passes the clip 421 and fastens with the sliding member 42 such that the clip 421 is pivotally connected to the sliding member 42. The clip 421 has a first (clipping) projection 4211 and a second (stable) projection 4214. The first (clipping) projection 4211 and the second (stable) projection 4214 pass the sliding member 42 and abut against the lean rail 4121. The clip 421 has a jointer 4214 formed therein. The jointer 4214 is a slot. The spring 414 is disposed between the fixing member 41 and the sliding member 42 to provide a resilient force. The inner rail 30 has a guiding member 32 corresponding to the jointer 4214. When the inner rail 30 is pulled outwardly, the guiding member 32 engages with the jointer 4214 such that the clip 421 and the sliding member 42 move together along the lean rail 4121. In the meantime, the intermediate rail 20 is driven to move in the outer rail space 11. In other embodiment, the guiding member 32 is a slot and the jointer 4214 is a projection corresponding to the slot. When the clip 421 moves in the hold slot 413, the first (clipping) projection 4211 and the second (stable) projection 4212 respectively engage with the hold slot 413 and the slot 413A such that the sliding member 42 fastens with the hold slot 413. In the meantime, the guiding member 32 disengages with the jointer 4214 and the inner rail 30 moves outwardly.

The sliding rail 412 is disposed in the avoiding space 23, such that the intermediate rail 20 is not blocked by the sliding rail 412, when the intermediate rail 20 moves in the outer rail space 11. The rail assembly further comprises a damping unit. The damping unit includes a damper 50 and a stopper 52 corresponding to the damper 50. The stopper 52 is disposed in the sliding member 42. In other embodiment, the stopper 52 is disposed in the sliding rail 412. The damper 50 is disposed in one end of the fixing member 41. In other embodiment, the damper 50 is disposed in the intermediate rail 20 or the avoiding space 23 to provide the function of damping.

The sliding member 42 moves in the outer rail space 11 due to the open type sliding rail 412 structure. The retracting travel of the sliding member 42 is increased, so is the moving range of the intermediate rail 20. The length of the intermediate rail 20 and the total span are increased.

The fixing member 41 has two avoiding slots 415 defined therein. The sliding member 42 also has two avoiding slots 422 defined therein. Each avoiding slot 415,422 is corresponded to the inner rail 30 to prevent the inner rail 30 from blocking. The inner rail 30 reaches the closed end of the outer rail space 11. The length of the inner rail 30 and that of the outer rail 10 are the same such that the total span and the loading capability are increased.

Referring to the FIG. 9, a resilient member 4213 is disposed in the clip 421. The sliding member 42 has a stopper 428 formed therein and corresponding to the resilient member 4213. When the clip 421 disengages the hold slot 413, the resilient member 4213 is provided to damp the clip 421. When the sliding member 42 engages the hold slot 413, the resilient member 4213 is provided to stable the engagement between the clip 421 and the sliding member 42.

Referring to FIGS. 10-12, the operation of the third embodiment of the rail assembly in accordance with the present invention is illustrated. When the inner rail 30 is pulled outwardly and extends to the sliding rail 412, the first (clipping) projection 4211 and the second (stable) projection 4212 respectively engages with the hold slot 413 and slot 413A such that the sliding member 42 is fastened with sliding rail 412. When the inner rail 30 is pushed back, the guiding member 32 engages with the jointer 4214 to push the clip 421. The clip 421 is rotated relative to the sliding member 42 such that the first (clipping) projection 4211 and the second (stable) projection 4212 disengage with the hold slot 413 and the slot 413A respectively. In the meantime, the sliding member 42 is subjected the resilient force provided by the spring 414 to retract. The sliding member 42 and the clip 421 move along the lean rail 4121. In the meantime, the sliding member 42 is subjected the damper force provided by the damper 50 to slow down.

Referring to FIG. 13, a resilient groove 4215 is disposed in a connection of the jointer 4214. When the sliding member 42 disconnects to the inner rail 30 carelessly and retracts automatically, user pushes the inner rail 30 to retract such that the guiding member 32 engages with the jointer 4214. The sliding member 42 restores to normal condition.

Referring to FIG. 14, a fourth embodiment of a rail assembly in accordance with the present invention is illustrated. The function and effort which are the same with the third embodiment are not described. Only the difference is described. In this embodiment, the sliding rail 412 is formed in the outer rail 10. The lean rail 4121 is separated to the fixing member 41. The sliding member 42 is movable received in the sliding rail 412. The sliding member 42 moves in the outer rail space 11 due to the sliding rail 412. The sliding member 42 has a sliding groove 429 defined in an underside thereof and corresponding to the lean rail 4121. When the inner rail 30 is pulled outwardly, the clip 421 and the sliding member 42 move along the lean rail 4121. In the meantime, the intermediate rail 20 moves in the outer rail space 11. The clip 421 selectively engages with the hold slot 413 and slot 413A. When the clip 421 moves in the hold slot 413 and slot 413A, the sliding member 42 is fastened by the hold slot 413 and slot 413A. The lean rail 4121 is movably received in the avoiding space 23, such that the intermediate rail 20 is not blocked by the lean rail 4121.

The sliding member 42 is movably received in the outer rail space 11 due to the open type sliding rail structure. The retracting travel of the sliding member 42 is increased, so is the moving range of the intermediate rail 20. The total span and the length of the intermediate rail 20 are increased.

Referring to FIG. 15, a fifth embodiment of a rail assembly in accordance with the present invention is illustrated. The function and effort which are the same with the third embodiment are not described. Only the difference is described. In this embodiment, the retrieving unit 40 includes a fixing member 41, a sliding member 42, a clip 421, and a spring 414. The fixing member 41 has a sliding rail 412 formed therein. The sliding member 42 has an extending groove 44 defined in an underside thereof and corresponding to the sliding rail 412. The sliding member 42 moves in the outer rail space 11 due to the sliding rail 412.

The sliding member 42 is movably received in the outer rail space 11 due to the open type sliding rail structure. The retracting travel of the sliding member 42 is increased, so is the moving range of the intermediate rail 20. The total span is increased due to the avoiding slots 415,422.

Referring to FIGS. 16-17, a sixth embodiment of a rail assembly in accordance with the present invention is illustrated. The function and effort which are the same with the third embodiment are not described. Only the difference is described. In this embodiment, the retrieving unit 40 includes a fixing member 41, a sliding member 42, a clip 421, and a spring 414. The fixing member 41 has a slot type sliding rail 45 defined in an underside thereof. The sliding member 42 has an extending rail 419 extended from one end thereof and corresponding to the sliding rail 45 such that the sliding member 42 moves in the outer rail space 11. The extending rail 419 has a slot 425 defined therein for movably receiving the second (stable) projection 4212 of the clip 421. The first (clipping) projection 4211 passes the lean rail 4121 and selectively engages with the guiding member 32. When the inner rail 30 is pulled out, the guiding member 32 engages with the clip 421 to drive the clip 421 and the sliding member 42 to move along the lean rail 4121. When the clip 421 moves in the hold slot 413, the first (clipping) projection 4211 engages with the hold slot 413 such that the sliding member 42 is fastened with the hold slot 413 temporarily. The inner rail 30 moves outwardly.

The sliding member 42 is movably received in the outer rail space 11 due to the open type sliding rail structure. The retracting travel of the sliding member 42 is increased, so is the moving range of the intermediate rail 20. The total span is increased due to the avoiding slots 415,422.

Referring to FIGS. 18-23, a seventh embodiment of a rail assembly in accordance with the present invention is illustrated. The function and effort which are the same with the third embodiment are not described. Only the difference is described. In this embodiment, the retrieving unit 40 further comprises a buckling unit. The buckling unit includes a buckling member 417 which connects fixing member 41 and the sliding member 42, a limited slot 423 defined in the sliding member 42, and a buckling portion 4231 formed in the limited slot 423. The buckling member 417 has a pivotal projection 4172 and a buckling projection 4171. The pivotal projection 4172 is pivotally connected to the fixing member 41 such that the buckling projection 4171 is rotated relative to the pivotal projection 4172. The buckling projection 4171 selectively engages with buckling portion 4231 such that the sliding member 42 fastens with the buckling member 417 to limit the movement of the sliding member 42 in the sliding rail 412. The springs 414 are disposed between the fixing member 41 and the sliding member 42 to provide the effort of retracting.

Referring to FIGS. 21-23, the operation of the rail assembly is illustrated. When user applies an external force on the inner rail 30, the inner rail 30 retracts in the outer rail space 11 and extends into the end of the outer rail 10. The guiding member 32 engages with the clip 421. The sliding member 42 abuts against the springs 414 and temporarily fastens with the fixing member 41. When the intermediate rail 20 and the inner rail 30 extend into the end of the outer rail 10, the buckling projection 4171 of the buckling member 417 protrudes into the limited slot 423 as shown in FIG. 21. The buckling projection 4171 is guided by the limited slot 423 to move the buckling portion 4231. When the external force is removed, the sliding member 22 is subjected the resilient force provided by the spring 414 to move toward the direction opposite to the fixing member 41 as shown in FIG. 22. The buckling projection 4171 engages with the buckling portion 4231 to limit the movement of the sliding member 42. The intermediate rail 20 and the inner rail 30 are stopped in the outer rail space 11. Referring to FIGS. 22-23, when user applies the external force again, the sliding member 42 moves toward the fixing member 41. The buckling projection 4171 is guided by the limited slot 423 and disengages with the buckling portion 4231. The sliding member 42 unfastened with the fixing member 41. The sliding member 42 is subjected the resilient force provided by the spring 414. The inner rail 30 moves along the sliding rail 412 and pops into the hold slot 413 in the lean rail 4121. The sliding member 42 stops in the hold slot 413. The inner rail 30 moves outwardly.

The sliding member 42 is movably received in the outer rail space 11 due to the open type sliding rail structure. The retracting travel of the sliding member 42 is increased, so is the moving range of the intermediate rail 20. The total travel (span) is increased due to the avoiding slots 415,422. The rail assembly has the effort of popping out.

Referring to FIG. 24, an eighth embodiment of a rail assembly in accordance with the present invention is illustrated. The function and effort which are the same with the third embodiment are not described. Only the difference is described. In this embodiment, the retrieving unit 40 includes a fixing member 41, a sliding member 42, a clip 421, and a spring 414. The fixing member 41 has a sliding rail 412 defined in free (one) end thereof. The sliding member 42 has an opening defined in a top thereof. The opening has two horizontal receiving grooves formed from a lean rail and a slot, respectively defined in a lateral thereof. The clip 421 has an Up curve-shaped. The Up curve-shaped clip 421 has a first projection 4211 extended from the bottom thereof. The Up curve-shaped clip 421 has a second projection 4212 extended from one end thereof near the fixing member 41. The clip 421 has a jointer formed in other end thereof away from the fixing member 41. The first projection 4211 and the second projection 4212 are corresponding to the horizontal receiving grooves 413A, 4121A. The clip 421 and the sliding member 42 are pivotally moved by the first projection 4211 and interacted with the hold slot 413. When the guiding member 32 in the inner rail 30 engages with the jointer 4214, the clip 421 slides into the hold slot 413 such that the sliding member 42 is fixed by the hold slot 413 and slot 413A. The sliding member 42 slides in the outer rail space 11 by the sliding rail 412, the lean rail 4121 and grooves 413A, 4121A. The sliding rail 412 is disposed in the avoiding space 23 in the underside of the inner rail 20.

Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed. 

1. A rail assembly comprising: an outer rail having an outer rail space defined therein for receiving an intermediate rail, an inner rail, and a retrieving unit; the intermediate rail movably received in the outer rail space, the intermediate rail having an intermediate rail space defined therein; the inner rail movably received in the intermediated rail space; characterized in that the retrieving unit disposed in one end of the outer rail space, the retrieving unit comprising: a fixing member disposed in the outer rail space to close the outer rail space; a sliding rail disposed in the fixing member, the sliding member having two lean rails formed therein, the two lean rails respectively having a hold slot and a slot defined therein; a sliding member disposed in the outer rail space, wherein the sliding member moves along the sliding rail and is movably received in the outer rail space; wherein the intermediate rail has an avoiding space defined in an underside thereof such that a length and a moving range of the intermediate rail are increased; a clip pivotally connected to the sliding member, the clip having a first projection, a second projection, and a jointer formed therein, the first projection and the second projection respectively corresponding to the one of the two lean rails, the jointer having a resilient groove; a guiding member disposed in the inner rail; wherein the guiding member temporarily engages with the clip to connect the inner rail and the sliding member; wherein the sliding member is driven to steadily move along the sliding rail by the clip; wherein when the clip moves into the hold slot, the first projection and the second projection respectively engage with the hold slot and slot such that the sliding member is temporarily engages with the hold slot to limit a movement of the sliding member; and at least one spring disposed between the fixing member and the sliding member; wherein the fixing member and the sliding member have two avoiding slots respectively defined therein; when the inner rail moves in the outer rail space, the inner rail passes the avoiding slots to reach a closed end of the outer rail such that a length of the inner rail is equal to that of the outer rail; the at least one spring is disposed in one of an outer side of the two avoiding slots to provide an effort of automatic retraction.
 2. The rail assembly as claimed in claim 1, wherein the sliding rail is disposed in free end of the fixing member and separated from the fixing member.
 3. The rail assembly as claimed in claim 1, wherein the sliding rail is formed from outer rail which is in free end of the fixing member; the at least one lean rail is disposed in free end of the fixing member and in the avoiding spaces in the intermediate rail such that the sliding member moves along the sliding rail.
 4. The rail assembly as claimed in claim 1, wherein the at least one lean rail is disposed in free end of the fixing member and separated from the fixing member.
 5. The rail assembly as claimed in claim 1, wherein the sliding rail is disposed in a lateral of the fixing member; the sliding member has an extending rail formed therein and corresponding to the sliding rail such that the sliding member moves in the sliding rail.
 6. The rail assembly as claimed in claim 1, wherein the sliding member has a receiving groove formed from a lean rail and a slot, defined therein for receiving the clip; at the underside of the sliding member is abutted against the lean rail; the clip has a first (upper) projection and a second (lower) projection; the first (upper) projection passes through the receiving groove and moves along the receiving groove, is connected to the guiding member; the second (lower) projection is abutted against the lean rail ; wherein when the first (upper) projection temporarily engages with the guiding member, the inner rail is connected to the clip such that the sliding member moves along the lean rails; the sliding member temporarily engages with the hold slot.
 7. The rail assembly as claimed in claim 1, wherein the sliding member has an opening defined in a top thereof; the opening has two horizontal receiving grooves formed from a lean rail and a slot, respectively defined in a lateral thereof and the sliding rail has one lean rail for receiving the clip; the clip has a Up curve-shaped; the Up curve-shaped clip has a first projections extended from the bottom thereof and a second projections extended from one end thereof near the fixing member; the clip has a jointer formed in other end thereof away from the fixing member; the first projections and the second projections are corresponding to the horizontal receiving grooves; the clip and the sliding member are pivotally moved by the first projections and interacted with the hold slot; wherein when the guiding member in the inner rail engages with the jointer, the clip slides into the hold slot such that the sliding member is fixed by the hold slot and slot; the sliding member slides in the outer rail space by the sliding rail and the lean rail; the sliding rail is disposed in the avoiding space in the underside of the intermediate rail.
 8. The rail assembly as claimed in claim 1, wherein the sliding rail is disposed in a lateral of the fixing member; the sliding member has an extending rail formed therein and corresponding to the sliding rail, the sliding member also has a receiving groove formed from a lean rail and a slot, defined therein for receiving the clip; a top of the sliding member is abutted against the lean rail ; the clip has a first (upper) projection and a second (lower) projection; the first (upper) projection passes through the lean rail and is connected to the guiding member; the second (lower) projection passes through the receiving groove and moves along the receiving groove; wherein when the first (upper) projection temporarily engages with the guiding member, the inner rail is connected to the clip such that the sliding member moves along the lean rails; the sliding member temporarily engages with the hold slot to limit a movement of the sliding member.
 9. The rail assembly as claimed in claim 1, wherein the sliding rail is disposed in free end of the fixing member; the fixing member, the sliding rail, the sliding member, the clip, and the spring are disposed in the avoiding space; the retrieving unit further has a second guiding member disposed in the underside of the intermediate rail and a second clip disposed in the intermediate rail and in the intermediate rail space; wherein when the guiding member in the inner rail temporarily engages with the second clip, the second guiding member engages with the clip which is over the sliding member; the inner rail and the intermediate rail are connected by the retrieving unit to drive the sliding member to produce an effort of automatic retraction such that the inner rail, the intermediate rail, and the outer rail have the same length to provide total span and great load.
 10. The rail assembly as claimed in claim 1, further comprising a damping unit, the damping unit including a damper and a corresponding mechanism for the damper to provide an effort of damping.
 11. The rail assembly as claimed in claim 1, further comprising a buckling unit, the buckling unit including a buckling member which connects fixing member and the sliding member, a limited slot defined in the sliding member, and a buckling portion formed in the limited slot, the buckling member having a pivotal projection and a buckling projection, the pivotal projection pivotally connected to the fixing member such that the buckling projection is rotated relative to the pivotal projection, wherein the buckling projection selectively engages with buckling portion such that the sliding member fastens with the buckling member; wherein when a force applied to abut the sliding member against the fixing member, the buckling member disengages with the buckling portion to separate the sliding member and the fixing member; wherein the sliding member is pushed outwardly by the spring and engages with the hold slot; wherein the buckling unit is provided to limit the movement of the sliding member.
 12. The rail assembly as claimed in claim 1, wherein the jointer has a resilient groove; when the jointer engages with the guiding member, the clip is connected to the inner rail to drive the sliding member to engage/disengage with the hold slot; when the sliding member pops out accidentally, the resilient groove retrieve the inner rail to engage the sliding member with the jointer to restore a normal state.
 13. A rail assembly comprising: an outer rail having an outer rail space defined therein for receiving an inner rail, and a retrieving unit; the inner rail movably received in the outer rail space; characterized in that the retrieving unit disposed in one end of the outer rail space, the retrieving unit comprising: a fixing member disposed in the outer rail space to close the outer rail space; a sliding rail disposed in the fixing member, the sliding member having two lean rails formed therein, the two lean rails respectively having a hold slot and a slot defined therein; a sliding member disposed in the outer rail space, wherein the sliding member moves along the sliding rail and is movably received in the outer rail space; a clip pivotally connected to the sliding member, the clip having a first projection, a second projection, and a jointer formed therein, the first projection and the second projection respectively corresponding to the two lean rails, the jointer having a resilient groove; a guiding member disposed in the inner rail, wherein the guiding member temporarily engages with the clip to connect the inner rail and the sliding member; wherein the sliding member is driven to steadily move along the sliding rail by the clip; wherein when the clip moves into the hold slot, the first projection and the second projection respectively engage with the hold slot and slot such that the sliding member is temporarily engages with the hold slot to limit a movement of the sliding member; and at least one spring disposed between the fixing member and the sliding member; wherein the fixing member and the sliding member have two avoiding slots respectively defined therein; when the inner rail moves in the outer rail space, the inner rail passes the avoiding slots to reach a closed end of the outer rail such that a length of the inner rail is equal to that of the outer rail; the at least one spring is disposed in one of an outer side of the two avoiding slots to provide an effort of automatic retraction. 